Catsiff has admitted the painting is a sign, but argues the city's sign code is unconstitutional.

He filed an appeal with the Washington State Court of Appeals, but it upheld the city's code.

Catsiff then tried taking the case to the Washington State Supreme Court, but it refused to hear the case.

And this morning, the U.S. Supreme Court announced it would not hear the case as well.

Catsiff's attorney Michael de Grasse, says Catsiff may file a lawsuit against the city - claiming that other signs and murals in the downtown area have not been subjected to the same sign code.

"Based on our investigation, it has never taken enforcement action against any other sign or mural that violates the city's sign code in similar ways, and this raises a question of due process and equal protection because of selective enforcement" said de Grasse.

Michael de Grasse says he may also use the selective enforcement argument as a way to reduce some of the penalties against Catsiff.

Since October 2010, the city has fined Catsiff $100 a day each the day the painting stays up.

So far, he owes more than $80,000.

Walla Walla's city manager says because Catsiff has exhausted all his legal options and the city's sign code still stands, he has 30 days to take the sign down.

If he does not, the city can paint over it.

The city manager says he will accept only full compliance with the penalty Catsiff has incurred.